In general, an auxiliary-machinery belt includes an auxiliary-machinery pulley such as a crank pulley and an alternator which are a driving source, a power steering, an air conditioner pump, a water pump, etc. connected through a belt, such that the alternator, the power steering, the air conditioner pump, the water pump, etc. may operate by a torque of the crank pulley transferred through the auxiliary-machinery belt.
Such an auxiliary-machinery belt needs to stably maintain a predetermined belt tension. For this, the crank pulley may include a toque filter (or a crank pulley damper) which reduces an instant speed change (irregularity) of the crank pulley based on four strokes of the combustion engine, thus improving stabilization of the belt tension.
The torque filter typically uses various methods in order to efficiently reduce an instant speed change (irregularity) by using a spring to simply set a threshold torque using a spring constant.
As an example of a spring type torque filter, there are a 1_stiff (1 stage stiffness) type torque filter having one arc spring arranged at left and right sides of an end stop (or travel stop) positioned at an inner side of inside a clutch spring and contacting with a hub. T2_stiff (2 stage stiffness) type torque filter has two arc springs arranged at the left and right.
Therefore, the 1_stiff and 2_stiff type torque filters may efficiently reduce the instant speed change (irregularity) of the crank pulley, thus stably maintaining a belt tension.
However, in the torque filter to which the arc spring is applied, the end stop comes into direct contact with a crank shaft and a fixed hub, so that impact-based noises may inevitably occur between the fixed hub and the end stop depending on the size of a threshold torque.
For an instance, since the end stop is pushed back by pressing the hub and pushes the clutch spring, the end stop may turn into overrunning at a threshold torque of a set value without impact-based noises occurring when the hub and the end stop contact. Since the end stop doesn't sufficiently push the clutch spring by pressing the hub at the threshold torque which is lower than a set value, a stop condition of idle stop and go (ISG) and an idle condition in which a load is applied from an alternator occur, and thus the end stop may not overrun, which may result in an occurrence of the impact-based noises.
In particular, for the 1_stiff type torque filter, the impact-based noises, which occur at the threshold torque lower than a set value under the stop condition and the idle condition in which a load is applied from the alternator, need to be eliminated. Further, a need exists to eliminate the impact-based noises occurring under the stop condition even in the 2_stiff type torque filter in which the impact-based noises may be eliminated under the idle condition in which load is applied from the alternator.